Inorganic Composition Modulation of Solid Electrolyte Interphase for Fast Charging Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• The solid electrolyte interphase (SEI) is crucial for lithium metal battery (LMB) performance.
• Lithium fluoride (LiF) SEIs offer stability but suffer from low Li ion conductivity, hindering fast charging.
• This limitation causes dendritic deposition and impedes practical LMB applications at high currents.

Purpose of the Study:

• To develop a novel SEI with enhanced Li ion conductivity for fast-charging LMBs.
• To address the limitations of LiF-based SEIs in terms of ion transport.
• To enable stable and high-performance operation of LMBs under demanding conditions.

Main Methods:

• Constructed a fluorophosphated SEI using a sol electrolyte with modified LiF nanoparticles.
• Incorporated phosphorus-containing functional groups to create fast ion-diffusing grain boundaries (LiF/Li3P).
• Demonstrated the presence of electrochemically active Li within these grain boundaries (GBs-Li).

Main Results:

• Achieved stable cycling of Li || NCM811 cells for over 1000 cycles at 5 C (11 mA cm-2).
• Fabricated a practical LMB pouch cell with high energy density (400 Wh kg-1).
• Demonstrated intrinsic safety and long cycle life under fast-charging conditions.

Conclusions:

• SEI component and structure design are key to enabling fast-charging LMBs.
• The fluorophosphated SEI with LiF/Li3P grain boundaries significantly improves Li ion conductivity.
• This approach facilitates the development of next-generation high-performance and safe lithium metal batteries.